Ancillary (or spectator) ligand-metal coordination complexes (e.g., organometallic complexes) and compositions are useful as catalysts, additives, stoichiometric reagents, monomers, solid-state precursors, therapeutic reagents and drugs. Ancillary ligand-metal coordination complexes of this type can be prepared by combining an ancillary ligand with a suitable metal compound or metal precursor in a suitable solvent at a suitable temperature. The ancillary ligand contains functional groups that bind to the metal center(s), remain associated with the metal center(s), and therefore provide an opportunity to modify the steric, electronic and chemical properties of the active metal center(s) of the complex.
One example of the use of these types of ancillary ligand-metal complexes and compositions is in the field of polymerization catalysis. In connection with single site catalysis, the ancillary ligand typically offers opportunities to modify the electronic and/or steric environment surrounding an active metal center. This allows the ancillary ligand to assist in the creation of possibly different polymers. Group 4 metallocene based single site catalysts are generally known for polymerization reactions. See, generally, “Chemistry of Cationic Dicyclopentadienyl Group 4 Metal-Alkyl Complexes”, Jordan, Adv. Organometallic Chem., 1991, Vol. 32, pp. 325-387 and “Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts”, Brintzinger, et al., Angew. Chem. Int. Ed. Engl., 1995, Vol.34, pp. 1143-1170, and the references therein, all of which is incorporated herein by reference.
One application for metallocene catalysts is producing ethylene copolymers. For example, PCT Application WO 00/37512 and published US patent application publication no. US 2001/0031843 A1 employ reaction product of zirconium tetrabenzyl and two equivalents of a phenol-triazole ligand with MMAO activation as catalyst for ethylene-hexene copolymerization (see Example 3). This application reports production of solid polyethylene, and states that the catalysts described are expected to produce HDPE (i.e., ethylene homopolymer) under ethylene-hexene copolymerization conditions (i.e., no incorporation of hexene).
As generally known to those of skill in the art of olefin polymerization, styrene is generally a more difficult comonomer to incorporate into an ethylene-α-olefin copolymer during copolymerization as compared with 1-hexene or 1-octene. See, e.g., Carlini et al., polymer 42 (2001) 5069-5078 (“The copolymerization of styrene with α-olefins by conventional Ziegler-Natta catalysts has been reported to occur with severe limitations.”) Moreover, most known ethylene styrene copolymers are directed toward polymers where the styrene is present in a chain terminating position (see, e.g., U.S. Pat. Nos. 3,390,141 and 5,180,872 and Pellecchia et al., Marcomolecules, 2000, 33, 2807-2814 and EP 0 526 943). There remains a need to find new ethylene-styrene copolymers and catalysts for such copolymers. In addition there remains a need for new polyolefin catalysts, in general.